1. Field of the Invention
The present invention relates to electrical connectors. More specifically, the present invention relates to array connectors, which can be a single-ended array connector or a differential pair array connector, which uses far fewer ground pins or blades and has a greater number of signal pins and achieves significantly improved electrical characteristics.
2. Description of the Related Art
It is known to provide an electrical connector, such as a board-to-board mezzanine connector, having a regular array of signal pins in a pin field. The signal pins must be surrounded by ground pins or ground blades or planes, which are provided both within the pin field and surrounding the pin field in order to prevent cross-talk between adjacent signal pins and to prevent EMI emissions from the pin field to the outside of the connector. For example, US 2003/0027439 A1, to Johnescu et al., teaches surrounding each of the signal pins with ground contacts or ground planes.
The use of so many pins as ground pins or the use of ground blades in between adjacent signal pins may increase the size of the connector, may decrease the number of signal pins that can be present in the connector, or both. If the size of the connector is reduced, then there is a corresponding reduction in the number of signal pins and signal to ground ratio.
These problems are especially difficult in a differential pair array connector where differential signals are passed through the connector.
In order to reduce crosstalk between adjacent differential signal pairs, typically a plurality of ground pins or ground planes are placed between the adjacent differential signal pairs. Although this arrangement results in better electrical performance, the overall signal pin density is decreased.
For example, as shown in FIG. 1, a connector includes a 7×7 array of pins 1 in a pin field. Each of the differential pairs 4 of signal pins 2 (indicated with crosshatching in FIG. 1) must be surrounded by ground pins 3 (indicated without crosshatching in FIG. 1) in order to provide proper shielding and prevent crosstalk between adjacent differential pairs 4. As a result, only six differential pairs 4 are possible in the 7×7 pin array of FIG. 1.
Typically, signal pins have a broader side and a narrower side, and when the broader sides of the signal pins of adjacent differential signal pairs are aligned with each other, much greater cross-talk occurs. In addition, the ground pins or ground blades must be arranged so as to surround the differential signal pairs to eliminate the disadvantageous broadside coupling between adjacent differential signal pairs. Thus, in such arrangements, ground pins or ground blades must be provided in between the adjacent differential signal pairs to attempt to minimize such disadvantageous broadside coupling.
As is clear from the above description, one of the unsolved problems of prior art array connectors is how to increase signal pin density without increasing the size of the connector or decreasing the quality of the electrical characteristics of the connector, and without complicating the arrangement of ground pins or ground blades.
Conventional array connector design dictates that the number of ground pins or ground blades cannot be minimized or eliminated without a concomitant increase in cross-talk and deterioration of electrical characteristics of the connector or PCB layout and/or routing. No suitable solution to this problem has been developed.
Another problem that occurs with such array connectors of the prior art is the use of so many ground pins requires a much more complex design and connection process for the PCB upon which the connector will be mounted and used. Because so many ground pins must be used in the pin field, a much greater number of PCB layers, traces, and vias must be used to properly route and connect the ground pins, which makes the PCB design and manufacturing process much more difficult, as well as, making the connection of the array connector to the PCB more difficult. Also, with the increased number of PCB layers, traces, and vias, there is much greater chance for having impedance mismatch problems, increased crosstalk, and greatly increased manufacturing complexity and overall design cost.
In addition, most array connectors have a unique signal arrangement and thus, require a unique ground arrangement. Thus, ground contacts and shields must be specially designed for each array connector, thereby requiring unique tooling and assembly equipment for each component of the connector. Also, the contact and terminal solder termination and retention features are non-uniform and different for each connector. This greatly increases the complexity and cost of manufacturing such connectors and related PCBs. That is, a standard pin arrangement and construction of an array connector cannot be adapted to various unique array connector designs.